ADMP521

Data Sheet

Rev. A | Page 12 of 16

ALTERNATIVE PCB LAND PATTERNS

The standard PCB land pattern of the ADMP521 has a solid ring

around the edge of the footprint that may make routing the

microphone signals more difficult in some board designs. This

ring is used to improve the RF immunity performance of the

ADMP521; however, it is not necessary to have this full ring

connected for electrical functionality. If a design can tolerate

reduced RF immunity, this ring can either be broken or removed

completely from the PCB footprint. Figure 17 shows an example

PCB land pattern with no enclosing ring around the edge of the

part, and Figure 18 shows an example PCB land pattern with the

ring broken on two sides so that the inner pads can be more

easily routed on the PCB.

Figure 17. Example PCB Land Pattern with No Enclosing Ring

Figure 18. Example PCB Land Pattern with Broken Enclosing Ring

Note that in both of these patterns, the solid ring around the sound

port is still present; this ring is needed to ground the microphone

and for acoustic performance. The pad on the package connected

to this ring is ground and still needs a solid electrical connection to

the PCB ground. If a pattern like one of these two examples is

used on a PCB, take care that the unconnected ring on the bottom

of the ADMP521 is not placed directly over any exposed copper.

This ring on the microphone is still at ground and any PCB traces

routed underneath it need to be properly masked to avoid short

circuits.

PCB MATERIAL AND THICKNESS

The performance of the ADMP521 is not affected by PCB

thickness and can be mounted on both a rigid and flexible PCB.

A flexible PCB with the microphone can be attached directly to

the device housing with an adhesive layer. This mounting method

offers a reliable seal around the sound port, while providing the

shortest acoustic path for good sound quality.